Elastomeric dispensing valve manufacture

ABSTRACT

A system for molding dispensing valves includes first and second mold sections, at least one of which is movable with respect to the other between a closed position in which the mold sections form a plurality of dispensing valve mold cavities, and an open position in which the mold sections are spaced from each other and the mold cavities are open along a mold parting line. A transfer mechanism is movable between the first and second mold sections in the open positions of the mold sections for receiving molded valves from the cavities and transferring the valves from between the mold sections.

The present invention is directed to manufacture of dispensing valves offlexible resilient elastomeric material, and more particularly to amold, a mold system and a method of making elastomeric dispensingvalves.

BACKGROUND AND SUMMARY OF THE INVENTION

Dispensing valves of flexible resilient elastomeric material,particularly liquid silicone rubber, are currently finding applicationin dispensing packages for a wide variety of fluid products such asbeverages, food condiments and body lotions. A package and a valve ofthis type are disclosed, for example, in U.S. Pat. No. 4,749,108.Current technology for manufacturing valves of this type involvesstamping the valve from a sheet of resin material when the material ispartially cured, so that the valve retains the shape imparted by thestamping operation following separation from the sheet. This techniqueinvolves significant waste of material, which cannot be recycled. Thevalves are coated with talc to prevent the valves from adhering to eachother, and the valves are placed in a vibrator bowl for orientationpurposes. Valves fed from the bowl, when properly oriented, are placedin closures for securement to containers after filling. It is thereforea general object of the present invention to provide an injection mold,a mold system and a method of making a dispensing valve that reduce theamount of scrap material and simplify handling of the valves as comparedwith the current technology described immediately above.

An injection mold for making elastomeric dispensing valves in accordancewith one aspect of the present invention includes a first mold sectionhaving a core plate with at least one core and a stripper plate havingat least one core passage in which the core is slidably received. Asecond mold section has a cavity plate with at least one passage forfeeding elastomeric material through the cavity plate. At least one ofthe first and second mold sections is movable with respect to the otherbetween an open position in which the first and second mold sections arespaced from each other, and a closed position in which the first andsecond mold sections are in facing engagement to form at least one moldcavity for molding a dispensing valve between the cavity plate on thesecond mold section, and the stripper plate and an end of the core onthe first mold section. The stripper plate has a vacuum passage forselective application of vacuum to the mold cavity and to a dispensingvalve molded in the mold cavity.

A system for molding dispensing valves in accordance with a secondaspect of the present invention includes a first mold section and asecond mold section, at least one of which is movable with respect tothe other between a closed position in which the mold sections form aplurality of dispensing valve mold cavities, and an open position inwhich the mold sections are spaced from each other and the mold cavitiesare opened along a mold parting line. A transfer mechanism is movablebetween the first and second mold sections in the open position of themold sections for receiving molded valves from the cavities andtransferring the valves from between the mold sections. The first moldsection in accordance with a preferred embodiment of this second aspectof the invention includes a plurality of vacuum passages for selectivelyapplying vacuum to valves in the mold cavities, first to retain thevalves in the cavities when the mold sections are separated and then topermit transfer of the valves from the cavities to the transfermechanism.

A method of making a dispensing valve in accordance with a third aspectof the present invention includes closing a mold having first and secondmold sections and at least one mold cavity formed at a parting linebetween the mold sections. A dispensing valve is injection molded in thecavity, and the mold sections are then separated along the parting linewhile applying vacuum to the cavity through the first mold section toretain the molded valve on the first mold section. The molded valve isthen contacted by a transfer mechanism, and vacuum is applied to thevalve through the transfer mechanism and releasing the vacuum applied tothe valve through the first mold section. The valve is then removed fromthe first mold section by the transfer mechanism. In the preferredimplementation of this third aspect of the invention, the valve isinjection molded of liquid silicone rubber and allowed to cure withinthe mold cavity prior to separation of the mold sections, so that thevalve retains its molded shape during transfer and further processing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objects, features and advantagesthereof, will be best understood from the following description, theappended claims and the accompanying drawings in which:

FIG. 1 is a functional block diagram of a mold system for injectionmolding liquid silicone dispensing valves in accordance with anexemplary presently preferred embodiment of the invention;

FIG. 2 is an elevational view of the upper and lower mold sections inthe system of FIG. 1;

FIG. 2A is an enlarged sectional view of the portion of FIG. 2 withinthe area 2A;

FIG. 3 is a fragmentary sectional view of a portion of the mold in FIG.2 at an intermediate stage of operation;

FIG. 4 is fragmentary sectional view of the mold in FIG. 2 at a secondintermediate stage of operation;

FIG. 5 is a fragmentary elevational view of the valve transfer mechanismillustrated schematically in FIG. 1;

FIG. 5A is an enlarged sectional view of the portion of FIG. 5 withinthe circle 5A;

FIG. 6 is a fragmentary sectional view of a portion of the mold andtransfer mechanism at a further stage of operation; and

FIGS. 7 and 8 are sectioned elevational views of exemplary dispensingvalves molded with the mold system of FIGS. 1–6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a mold system 20 in accordance with an exemplary butpresently preferred implementation of the invention. Mold system 20includes an injection mold 22 having a first or lower mold section 24and a second or upper mold section 26. Upper mold section 26 receivesmoldable elastomeric material, such as liquid silicone rubber (LSR),from a gated manifold system or cold deck 28, which can be mounted onthe upper side of upper mold section 22. An air/vacuum control 30 iscoupled to lower mold section 24 and to a valve transfer mechanism 32.Mold sections 24,26 and transfer mechanism 32 are also connected to amotion control system 34, which may be electrical, hydraulic, pneumatic,or a combination thereof. In general, liquid silicone rubber or othersuitable moldable elastomeric material is injected through upper moldsection 26 into mold cavities between mold sections 24, 26, anddispensing valves are molded in the mold cavities. The mold sections arethen opened by motion control 34, and transfer mechanism 32 ispositioned between the open mold sections over the lower mold section.Vacuum is applied to the lower mold section to retain the molded valveson the lower mold section as the upper mold section is raised. Whentransfer mechanism 32 is positioned over lower mold section 24, vacuumon the valves through lower mold section 24 is released, and vacuum isapplied to transfer mechanism 32. Release of the valves from lower moldsection 24 may be effected by application of atmospheric air aftertermination of vacuum application, or more preferably by application ofair under pressure to assist pick-up of the valves by transfer mechanism32. Transfer mechanism 32 is then moved to a position over a pluralityof carriers 36, and vacuum is released at the transfer mechanism. Onceagain, transfer of the valves from transfer mechanism 32 to carriers 36may be effected by application of air at atmospheric pressure attransfer mechanism 32, or further assisted by application of air underpressure. The valves are transported by carriers 36 for furtherprocessing, including formation of one or more dispensing openings inthe valve and placement of the valve in a closure or container.

Mold 22 is illustrated in greater detail in FIGS. 2 and 2A. Second orupper mold section 26 includes a cavity plate 40 on which a cavity block42 is mounted. At least one cavity insert 44, and preferably a pluralityof cavity inserts 44, are mounted in a spaced array on cavity block 42.A plurality of passages 46 extend from cavity inserts 44 through cavityplate 40, a cavity backing plate 48 and an insulator board 50 to receiveliquid silicone rubber (LSR) (or other suitable elastomeric material)from suitable valve gates on runner system or cold deck 28 (FIG. 1).Each cavity insert 44 includes an opening 52 (FIG. 2A), preferablycentrally located on the cavity insert, for feeding the elastomericmaterial to the associated mold cavity 70 (FIG. 2A), which is defined inpart by the lower surface of the cavity insert. (Directional words suchas “upper” and “lower” are employed by way of description and notlimitation with respect to the orientation of the mold sectionsillustrated in the drawings.)

First or lower mold section 24 includes a stripper block 54 carried by astripper plate 56 for opposed facing engagement with cavity block 42 onupper mold section 26 along a first mold parting line 58. A core plate60 is mounted on a core backing plate 62. At least one mold core 64, andpreferably a plurality of mold cores 64, are mounted on and extendupwardly from core plate 60 in a parallel spaced array. Each mold core64 is slidably received in an associated mold core passage 66 thatextends through stripper plate 56 and stripper block 54. Core plate 60abuts stripper plate 56 along a second mold parting line 68. As bestseen in FIG. 2A, a mold cavity 70 is formed at parting line 58 betweenthe lower face of each cavity insert 44, the upper face of each moldcore 64 and the upper edge of the inner periphery of each mold corepassage 66 in stripper block 54. A vacuum passage 72 is connected toeach mold core passage 66 adjacent to the upper end of the mold corepassage in stripper block 54. Each vacuum passage 72 is connectedthrough stripper block 54 to a vacuum manifold passage 74 that extendsthrough stripper plate 56, and is connected to air/vacuum control 30(FIG. 1) through one or more appropriate fittings on stripper plate 56.Heater elements 76 are also carried by core plate 60, stripper plate 56,stripper block 54, cavity block 42 and cavity plate 40 for energizationas required to maintain a desired mold temperature. Core backing plate62 is biased upwardly by a plurality of springs 78 that engage anejector box 80. Ejector box 80 is mounted on a clamp plate 82, which issecured in fixed position in the preferred implementation of theinvention.

With mold sections 24, 26 closed against each other as illustrated inFIGS. 1, 2 and 2A and with cores 64, core plate 60 and core backingplate 62 in their fully raised positions illustrated in FIGS. 2 and 2A,elastomeric material such as liquid silicone rubber is injected throughpassages 46 and cavity inserts 44 into mold cavities 70 formed betweenthe mold sections. The mold sections are maintained at elevatedtemperature, such as on the order of 320° F., and the valves in the moldcavities are allowed to cure sufficiently so that the valves will retaintheir shape upon removal from the mold. For liquid silicone rubber,sufficient curing takes place in about eight seconds at 320° F. Afterthis time, core backing plate 62, core plate 60 and cores 64 are loweredto the position illustrated in FIG. 3, in which the core platesubassembly abuts a stop 84 on ejector box 80. Core plate 60 thusseparates from stripper plate 56 along mold parting line 68, and pullsmold cores 64 downwardly in associated mold core passages 66. Thisdownward movement of the mold cores couples vacuum passages 72, whichwere previously blocked by the mold cores, to the valves 86 (FIG. 3) inthe mold cavities. Vacuum is applied to passages 72 through manifoldpassages 74 to retain valves 86 in position. With the molded valves soheld in position on lower mold section 24, upper mold section 26 is thenmoved upwardly to the position illustrated in FIG. 4 to allow access oftransfer mechanism 32 (FIG. 1) between the mold sections.

Transfer mechanism 32 is illustrated schematically in FIGS. 5 and 5A. Atransfer plate 86 carries a plurality of valve grippers 88. Each valvegripper 88 includes a stem 90 and a cup 92 mounted on the lower end ofthe stem. Each stem and cup have a through passage 94 that is connectedby a suitable conduit 96 to one of several vacuum manifolds 98 carriedon plate 86. These vacuum manifolds 98 are connected to air/vacuumcontrol 30 (FIG. 1). A plurality of locator pins 100 are positioned onplate 86 for cooperation with corresponding apertures 102 (FIG. 6) inlower mold section 24 for locating the transfer mechanism with respectto the lower mold section during valve transfer.

Referring to FIG. 6, and with upper mold section 26 fully retracted,transfer mechanism 32 is positioned by motion control 34 (FIG. 1) overthe upper face of lower mold section 24. Pins 100 on plate 86 arereceived in corresponding apertures 102 on lower mold section 24accurately to locate the transfer mechanism with respect to the lowermold section, so that the cup 92 of each gripper 88 is in facing contactwith a corresponding molded valve 86 carried on lower mold section 24and held on the lower mold section by application of vacuum throughpassages 72. With the transfer mechanism and grippers so positioned,vacuum is applied by control 30 (FIG. 1) to grippers 88 throughmanifolds 98 on transfer mechanism 32. At the same time, vacuum isreleased at vacuum passages 72 in lower mold section 24. This vacuumrelease may comprise simple connection of the vacuum passages toatmospheric air, thereby releasing the vacuum and allowing the valves tobe removed. Such release of vacuum more preferably is accompanied byapplication of air under pressure to vacuum passages 72 in the lowermold section to cooperate with application of vacuum at the transfermechanism to assist removal of the valves from the lower mold section.In any event, with the molded valves now held by grippers 88 on transfermechanism 32, the transfer mechanism is moved by control 34, such as asuitable robot control mechanism, to position the valves over carriers36 (FIG. 1). Application of vacuum at the transfer mechanism is thenterminated to allow the valves to fall by gravity onto associatedcarriers 36. This valve transfer from mechanism 32 may be assisted byapplication of air to grippers 88 through manifolds 98 on the transfermechanism. In the meantime, with the transfer mechanism withdrawn frombetween the mold sections, the mold sections may be returned to theclosed position of FIG. 2, and the cycle repeated.

FIGS. 7 and 8 illustrate exemplary dispensing valves 86 that can befabricated in accordance with the present invention. Valve 86, and usethereof in a dispensing package, is described in greater detail incopending U.S. application Ser. No. 10/164,948 filed Jun. 7, 2002 andassigned to the assignee hereof. The illustrated geometries of valve 86are merely exemplary, and other valve configurations can readily befabricated in accordance with the present disclosure.

The mold, system and method so described possess a number of significantadvantages. Waste material is significantly reduced in that the valvesare individually molded rather than cut from a sheet. Furthermore, thevalves are molded and transferred separately, eliminating any need forapplication of talc or the like, or use of a vibrator bowl or the like,to separate the valves for application to containers. The valves may bemolded in high volume, with each mold 22 containing ninety-six valvemold cavities, for example. Application of vacuum to the lower moldsection at the position of FIG. 3 may be monitored to confirm presenceof valves in all of the mold cavities. The entire operation can bereadily automated with limited operator supervision required. Theinvention has been described in conjunction with a presently preferredembodiment thereof, and a number of modifications and variations havebeen discussed. Other modifications and variations will readily suggestthemselves to persons of ordinary skill in the art. The invention isintended to embrace all such modifications and variations as fall withinthe spirit and broad scope of the appended claims.

1. An injection mold for making elastomeric dispensing valves, whichincludes: a first mold section having a core plate with at least onecore extending from said core plate and a stripper plate having at leastone core passage in which said at least one core is slidably received,and a second mold section having a cavity plate with at least one resinpassage for feeding elastomeric material through said cavity plate, atleast one of said first and second mold sections being movable withrespect to the other between an open position in which said first andsecond mold sections are spaced from each other, and a closed positionin which said first and second mold sections are in facing engagement toform at least one mold cavity coupled to said at least one resin passagein said second mold section for injection molding a dispensing valvebetween said cavity plate on said second mold section, and said stripperplate and an end of said at least one core on said first mold section,said stripper plate having at least one vacuum passage for selectiveapplication of vacuum to said at least one mold cavity and to adispensing valve molded in said cavity.
 2. The mold set forth in claim 1wherein said core plate is movable with respect to said stripper plateto retract said end of said at least one core from said at least onecavity, and wherein said vacuum passage in said stripper plate iscoupled to said at least one core passage adjacent to said cavity suchthat said vacuum passage is coupled to said cavity upon retraction ofsaid end of said core from said cavity, said vacuum passage beingblocked from said cavity when said end of said core is disposed in saidcavity.
 3. The mold set forth in claim 2 wherein said core plateincludes a plurality of said cores, said stripper plate includes aplurality of said core passages and a plurality of vacuum passagescoupled to said core passages, and said cavity plate includes aplurality of resin passages that are coupled to the mold cavities in theclosed position of the first and second mold sections.
 4. The mold setforth in claim 1 including a transfer mechanism movable between saidfirst and second mold sections in said open position of said moldsections for receiving molded valves from said mold cavities andtransferring said valves from between said mold sections.
 5. The moldset forth in claim 4 wherein said transfer mechanism includes aplurality of second vacuum passages, a plurality of valve-contactelements coupled to said second vacuum passages, and means forselectively applying a vacuum to said second vacuum passages and thenceto said valve-contact elements to pick-up valves from said first moldsection, and for selectively releasing vacuum from said second vacuumpassages and thence to said valve-contact elements to separate valvesfrom said transfer mechanism.
 6. The mold set forth in claim 5 furthercomprising a plurality of valve carriers for individually receivingmolded valves from said transfer plate upon application of air to saidsecond passages and said elements for maintaining said valves out ofcontact with each other.